Study links status to health

New Delhi, April 11: Social rank appears to influence the activity of genes in female macaques, according to a new study that scientists say reveals a deep connection between social status and health.

Researchers in the US have found that gene activity levels, or expression levels, in a class of blood cells with a key role in the immune system are altered by the social ranks of female rhesus macaque monkeys.

Their study, published earlier this week in the US journal Proceedings of the National Academy of Sciences, has shown that lower-ranking monkeys displayed signs of exposure to chronic stress and had lower levels of a certain type of an immune cell.

“Social rank is a strong predictor of psychosocial stress which, in turn, seems to influence the expression of certain genes,” said Jenny Tung, an assistant professor at Duke University and lead author of the study.

Social hierarchies have been earlier shown to influence gene expressions in insects and fish. Queen bees, for example, show differences in patterns of gene expression than those observed in worker bees.

But Tung and her colleagues said their observations in a non-human primate species may have implications for how the stress of low socio-economic status affects the health of humans.

While the social hierarchy in groups of macaques the US researchers studied is quite different from the social environment observed among human populations, scientists point out that humans may have different sources of social stress.

“In humans, factors such as social isolation or low socio-economic status may lead to similar social stress experienced by the macaques with low social rankings,” Tung told The Telegraph in a telephone interview.

The macaques that the researchers studied were born and bred at the Yerkes National Prime Research Centre at Emory University in the US, but are likely to have originated from macaques from India sent to the US decades ago.

Macaques live in groups and, for this study, the scientists took female macaques from their native groups into new social groups where their ranks were determined by how early a female was introduced into the unit.

The gene scans show that immune system activity changes with social ranks. “Our study supports the idea that low social status can be bad for the body, but it hints ... that if you improve your social situation, your health improves too,” Tung said in a statement issued through Duke University.

“This is a remarkable study,” said Anindya Sinha, a primatologist at the National Institute of Advanced Studies, Bangalore, who is studying wild macaques but was not connected with the US research.

“We’ve noticed even in the wild that changes in social status lead to changes in the physiology of the animals, but the connection between the two has not been made as clearly as this study does,” Sinha said.

“What is also exciting is that from the changes in gene expression, the scientists could even predict the social rank of the female — this shows the stability of these changes,” he added.

The US researchers said the study was designed to eliminate differences in the environment that might also influence gene expression. “The macaques were fed the same diet, they received the same level of veterinary care, and they had the same physical settings,” Tung said. The results highlight the important connection between social status and changes at the genetic level.